None
Not applicable.
1. Field of the Invention
This invention relates to tools for manual finishing of surfaces using coated abrasives, particularly those that combine a variety of kinds of abrasive coatings and grit sizes within a single tool.
Primitive abrasion processes used stones and loose sand for shaping and smoothing. Modern processes for finishing surfaces still employ tools with abrading materials of different fineness or abrasive nature. These tools include grinding wheels, whetstones, machinists"" files, and wood rasps. Flexible versions of this class are lens-shaping grit holders, emery boards, and sheets or belts of coated abrasives.
A coated abrasive is a combination of mineral grits and a bonding material coated upon one surface of a substrate, sometimes called a backing. Usually the opposite surface of the substrate is not so coated. Manual coated abrasive finishing operations are those that do not use power tools and involve simply rubbing an abrading grit surface upon work areas that may range in size from a single edge to several square meters. Such manual operations include brief tasks, such as clearing splinters from a freshly sawed piece of wood, removing sharp edges from cut metal, and shaping fingernails, as well more elaborate tasks, such as smoothing a patched or damaged automobile paint surface and preparing furniture for application of stain, oil, or varnish.
Typically, a coated abrasive finishing process first uses a relatively coarse grit of a type specific to the work piece, followed by a similar process using at least one finer grit. Each step finer in grit size smooths scratches made by its predecessor step. Using many small steps in grit size reduces the amount of working needed with each one. There are about twenty commercially available grit sizes, covering the whole range of shaping, smoothing, and polishing. The grit size designations correspond to those used in the manufacture of grinding wheels. The American National Standards Institute maintains, under the general category B-74, definitions of standard numerical grit sizes. In other countries analogous standards have also evolved. Coated abrasive sheet descriptors may also designate methods or materials of manufacture.
Commercially packaged coated abrasives have commonly displayed the descriptive terms xe2x80x9ccoarse,xe2x80x9d xe2x80x9cmedium,xe2x80x9d and xe2x80x9cfine.xe2x80x9d The meanings of these particular words have differed, however, for different minerals and fields of application. For example, some aluminum oxide based coatings designed for wood working have had a grit size of 120 and carry the descriptor xe2x80x9cfine.xe2x80x9d Silicon carbide based coatings of the finer grit size 320 used for automobile finishing have been labeled xe2x80x9ccoarse.xe2x80x9d Therefore, there is a need for labels on coated abrasives that will disclose not only the grit size but the abrasive mineral content as well. Moreover, it can be a significant convenience to the user to combine several grit sizes and/or several kinds of mineral abrasive into a single manual abrasive tool; this is especially helpful for experimenting on a small portion of a work piece with various grit sizes and kinds of coated abrasives to determine the optimal combination to use.
U.S. Pat. No. 27,817, issued in 1860 to T. J. Mayall, described an abrasive sheet first formed by combining a xe2x80x9cvulcanizablexe2x80x9d rubber compound and grit, and adhering the combination to a backing, followed by vulcanizing the backing. This was alleged to provide an improvement over emery-cloth, emery-paper, and sand-paper.
U.S. Pat. No. 81,986, issued in 1868 to J. H. Crane, disclosed two coated abrasive sheets of different grit sizes adhered together, forming a single flexible article coated on both surfaces.
U.S. Pat. No. 357,412, issued in 1891, to E. A. Dubxc3xa9y, disclosed a single sheet of xe2x80x9csand-paper or the like,xe2x80x9d with several different grades of abrading substance directly coated upon its substrate or backing surface in distinct sections. The coated sections were separated by narrow creases that were not coated with abrasive. Depicted in the Dubxc3xa9y patent is a sheet with six such sections of identical rectangular size, folded once. This was then Z-folded to form a packet, providing a choice of different grits as the abrading face. These multiple thick folds in the packet created a versatile, unlabeled tool, but using the sheet, without folding it, was inherently clumsy. Even now, it would probably not be economic to coat uniformly the different areas as depicted in Dubxc3xa9y""s patent upon the same substrate or backing. Creation of uniform, high quality abrasive coatings on a mass scale usually entails a continuous-coating manufacturing process, with a controlled coating composition. Dubxc3xa9y""s sheet had no identification for individual grades or sizes of grit or any other identification marking. The composition and configuration of different grit sizes could not be altered by the end user. Neither the packet thickness nor the sheet size in Dubxc3xa9y""s sheet allowed conveniently applying force directly upon a work piece surface through only a single layer of coated abrasive. This eliminated an occasional advantage in shaping the workpiece provided in the flexible, single sheet abrasive tools disclosed by Mayall and Crane.
A three dimensional, multi-grit, coated abrasive article for manual finishing was described in U.S. Pat. No. 1,146,359 issued to W. D. Smith in 1915. It was shown as a trifoliate structure of three (or more) rectangular leaves connected along a single axis where they were joined. Each leaf had coated abrasive on both surfaces, so that all exposed surfaces were coated abrasive. The leaves folded together, and they could also be applied individually to a workpiece. Exposing the workpiece to two leaves at once was noted as an advantage, and adjacent leaf surfaces could be formed by a single folded sheet. Grit size variety was not explicitly mentioned, and there was no consideration given to grit size identification. Construction details mentioned the reinforcing effect of forming a leaf by cementing two pieces of ordinary coated abrasive paper together.
An improvement in removable abrasive and polishing sheets and pads for use with power tools was described in U.S. Pat. No. 4,437,269, issued to G. Shaw in 1984. The removable feature was achieved by adhering a textile layer with filament loops to the non-grit surface of a mass-manufactured abrasive sheet or disk. These loops were releaseably engaged by suitable hooks or stalks mounted on the tool face. A transparent adhesive was used, and the textile layer itself was selected to be sufficiently transparent to allow reading indicia already imprinted on the non-grit surface of these sheets by the coated abrasive manufacturer.
U.S. Pat. No. 5,140,785, issued to B. Eleouet, disclosed a scouring pad combination comprising several different pads of comparable but different thicknesses and attached to a flexible connecting sheet that formed hinges between the pads. In use, a packet of cleaning pads was folded into a conveniently held block through which force was applied. No provision was made for identification markings inasmuch as abrading composite or polishing material was attached to opposite surfaces of the connecting sheet.
Users of coated abrasives for manual finishing may not be experts in the many kinds of abrasives available, but they are resourceful people. Whether occasional or frequent users, they need grit variety, identification information, adaptability, predictable quality, and convenience in use and storage.
There remains a need, therefore, for an abrasive tool for manually finishing small surface areas that displays by indicia at least the grit size and abrasive mineral content. Such a tool preferably comprises reinforced, coated abrasive pieces with several grit sizes, arranged in an ordered sequence to facilitate experimentally determining the most effective grit choices for finishing a particular work piece. The tool should be easily modified, customized, shaped, or repaired, even by occasional users, and should be compact and portable. A simple and inexpensive method for making such a tool is also desirable. These needs are fulfilled by the present invention.
A multi-grit tool for manual finishing comprises coated abrasive pieces connected by fully pliable hinges that allow each piece to be applied to a work surface individually. A distinctive labeling addition to the non-grit surface of each abrasive piece includes indicia that characterize the abrasive nature of its grit surface, including at least the grit sizes and the type of mineral abrasive. The labelling addition may serve other functions as well, such as suggesting uses for the tool and displaying advertising copy. In one embodiment, the abrasive pieces are arranged in linear array, and in order of increasing grit size; in this embodiment, the tool accordion-folds into a compact packet. In an alternative embodiment, two or more pairs of hingedly-connected abrasive coated pieces are joined along a common hinge line to form a booklet. A preferred method for forming the hinges includes the step of attaching a continuous strip of transparent adhesive tape to the non-grit surfaces (directly over the distinctive labeling additions thereon) of a plurality of linearly aligned, abrasive coated pieces, such that the portions of the tape between the pieces form the hinges.